Vulcanization accelerator



Patented Mar.' 7,'1939 I a I I Q IT S E 1 2,149,859 ACCELERATOR Chat-1e50,. MiserentinoQBufiaio; N. Y.', as signor i r' togDunlop Tire and Rubber Corporation, Bufo htalo,,N .Y., a corporation of lIew York y I i No Drawing. Application 15; 1937;; Serial No. 142,876 .n a isciaims'l romeo-2'10 v f This application is a continuation in part of radicals or may constitute different carbon atmy (to-pending application Serial 11'0141379' filed Oms of an organic radicaL -a'nd R3 is the mono- September 20, 1935. p f y basic organicacid minus the hydrogen displaced My present invention relates ,toman accelerator when the acid combines-with a base. The NH4 7 of vulcanization, more particularly; to an accelradical y be Substituted-by y Suitable metal a. erator that will enable vulcanization to be ac- Such s Zinc, m, magnesium, calcium, complisiied at a relatively low temperature as,.for The monoebasic dx t a v ompo d may example, at the temperature of boiling water. be analiphatic or an aromatic acid, For e'x- Morerparticularly the invention relates to an p it y be a Straight Chain aliphatic acid '10 acceleratorfor usein making cellular rubber by a h -S c Stearic, p c, pri cap process of foaming n aqu ou di si of acetic, laurie etc., acids, or it may be an aromatic rubber and thereafter vulcanizing the foamed, acid such as benzoic acid 'or mercaptobenzbthi-j structure A azole-(captax). Such acids as cinnamic acid, or Heretofore, ultra-acceleratorsrhave'been used other a c acids having a Side Chain might '15 in vulcanizing such foamed rubber structures be used. p ".15 because vulcanization is preferably accomplished y suitable Secondary amine m y be mp oy d atthe boilingpoint of waten generally in con- F Ew e fa V v tactv withjboiling waterors'te'am; Manyof t e v T if j e H Bf' l ultra-accelerators are not"sufliciently rapid to H H a i 120 accomplish .the lcaniz'ation of the ioariied 1 1 I l\ 9 '20 structureat the,low texnperaturesusedgn I p I y p A Som ultra-accelerators that mightlbefused at For example; it may be a secondary aliphatic the temperatures desirable for the vulcanizing amine such as dimethyl amine; diethyl amine, die

of a rubber foam have a tendency to break down propyl amine or a methyl ethyl amine, methylthe foam or froth of the aqueous dispersion while 'propyl amine; ethylpropyl amine,{etc., or it may 25 it -is;beingformed,;or while it isbeing set or gelled be a secondary aromatic amine such 7 as-cliand thus impair or change the structurebefore phenyl amine, 'or'it rnay'b'e a heterocyclic'amin'e, vulcanization is possible, In many cases, the Oranyalnine in which 'twovalences-of the nitropresence of the accelerators heretofore available gen atom are specified or taken up by one or tw will prevent the formation of the froth or foam. 7 o ganic compounds. My present invention overcomes the abovedis- For example, it may be piperidineadvantages and-provides an acceleratorwhich H H will rapidly cure the rubber froth or foam at a v v \d/ 1 f sufliciently low temperaturesuch, for example,'as

the temperature-of boiling water, and which will V v HN CH2 v '35 not impair or destroyfthe structure of the foamed l i latex. Q v 1 Y v/"\ The accelerator of my invention is a reaction 2 product of a secondary amine and mono-basic formmg'the compoundof my mvention the 4 organic acid and carbon bisulphide orga saltof m F f fis d c m i -wi h e se nda ,40

such reaction product with a metal; The reacamm m n n t ih 'IO a iQn 0f tionpr'oduct has the getier'alformula- -.amm.on m' j i a d hydro- 1 Y 3' v k; 4 chloric acid, the valence of the nitrogen atom V I 5? 23 i jchanging froni'3 m5; Thenthecompoundthus 5 o v p I .B:N.;.1 y. j .formedismixedwithcarbon"bisulphide, where- .F a upon the carbon atomof, the carbon bisulphide =8 I displaces one of the hydrogen atoms" combined v 1 with the nitrogen atom soflthat the carbon and N L I nitrogenare directly combined, and the displaced Invthe above :dmuemeba are organic hydrogen then' combined with'one'of the sulphur atoms of the carbon bisulphide group. Ammonia added to the resulting compound combines with the hydrogen and sulphur oi the compound. This ammonia may be replaced with any suitable metal suchas zinc, calcium, magnesium, sodium, potassium, etc.

Example I The following is an example of a preferred method of forming the accelerator 0! my invention. 240 grams of water and 40 grams of oleic acid added to the solution. The mixture is stlrred I .until the oleic aciddiss'olvesi. This will require about fifteen minutes; The reaction between the diethyl amine and the oleic acidmay be repre-.

The combined proportions will be determined by i the molecular weight as, for example, 284 parts sented by the following equation:

(cimhNnwnnacoon (carom 10.4 gramsoi carbon bisulphide are then added and the mixture stirred for an additional-fifteen t a The reaction may be represented as minutes, follows o o QCnHa o o c'c H" an V 1 g The resulting solution contains the accelerator and may be incorporated inan aqueous dispersion to be foamed and vulcanized to a permanent cellular structure. For example, the solution may be added to the aqueous rubber dispersion in the proportion of 20 grams of the solution for each 100 grams of dry rubber content in the dispersion.

I Otherstraight chain organic acids may be substituted. for oleic acid in whole or in part merely by using a weight of; the acid having the same relation to the quantity of oleic acid as the V relation of their molecular weight, it being un derstood that when acids of lower molecular weight are employed, a proportionately lower weight maybe used when substituted for oleic acid. It will also be understood that diethyl amine has been'mentioned. merely" by way of exampleof a' secondary amineuseful in the process, but

it will be understood that other secondary amines, such as dimethyl amine or dipropyl' amine might be used in place ofdiethyl amine. T form the corresponding metal salt, it is merely necessary to add zinc chloride'or other salt, or to add a suitable hydroxide such as sodium or potassium hydroxide.

10 grams of diethyl amine are dissolved in OOCCi'IHu Example II Diphenyl amine may be combined'with stearic acid according to the iollowing equation:

. I I I CH a N CnHuCOO-Irl stearic acid diphenylamine of stearicuacidto about 169 parts of the diphenyl amine. The resulting compound is then reacted with one molecule of carbon bisulphide (76 parts.)

i I Example lII Piperidine, a heterocyclic secondary amine, is

I ooocnnn combined with stearic acid according to the following equation: a

The combined weights may be calculated from the molecular formulae; for example;'85' parts jot pipe'ridineto 284 parts orstearic acid. Theresulting compoundgmay then be reacted'with 76 parts of carbon bisulphide and with ammonia, or

the hydroxides of zinc, 1 magnesium, potassium.

calcium, etc. V V

. j Eoiample 1 1 H An aromatic mono-basic acid, mercaptobenzothiazole, may be combined with fa secondary amine according to the following equation 'I'hat is, in the proportionszof ld'l parts ofmer captobenzothiazole to .83 parts 01 diethyl amine.

The resulting compound may then be combined with carbon bisulphide" ('l6 parts), and then with any suitable metal 'or ammonium.

In each ofthe above reactions the carbon of. the carbon bisulphide combines with the nitrogen atom of the compound resulting from the reactions represented by the equations. For example, diphenyl, dimethyl, dipropyl, etc., amines may be substituted in the reaction with the mercaptobenzothiazole, or a heterocyclic amine such piperidine, may be combined with other acids than stearic as, for example, palmitic, oleic, benzoic, cinnamic or mercaptobenzothiazole. Other heterocyclic amines may be employed instead of the piperidine as, for example, pyrrol.

iNhile these various compounds may be employed, the simpler compounds are quite satis' factory and may be more pleasant to work with and are, therefore, preferred.

Through my invention, therefore, I have provided a large number of accelerators suitable for low temperature vulcanization and having properties particularly desirable in the production of foamed latex compounds. They may, however,

be employed in various rubber compositions where vulcanization at low temperatures, or moderate temperatures, such as that of boiling water, or somewhat above, is desired. In such cases, the accelerator may be admixed with the rubber preferably in the form of latex or an'aqueous dispersion and, upon' gellingor setting, vulcanization may be accomplished by heating in 'boil-.

ing water or in steam, or inany suitable medium at the vulcanization temperature.

, What I claim is 1. The compound RI"N in which is an organic group having two carbon atoms separately joined to the nitrogen atom to form a secondary amine, in which R3 is a mono-basic organic acid radical, and R4 is a member of the group consisting of the metals usually used in rubber, hydrogen and ammonium. I

2. The compound of claim 1 in which is a secondary aliphatic amine.

6. The compound of claim 1' in which is a secondary amine of difierent organic radicals.

7. The compound of claim 1 in which 1 in which R:

Hill

is an aliphatic secondary amineand R3 is mer' captobenzothiazole.

13. The compound of claim 1 in which E R1 N is' piperidine, and R3 is a radical of a higher fatty acid. f

14. The process of making a vulcanization accelerator which comprises reacting a mono-basic organic acid with a secondary amine, and then reacting the resulting reactioncompound with carbon bisulphide.

15. The process of making a vulcanization accelerator which comprises reacting a mono-basic organic acid with a secondary aromatic amine, and then reacting the resulting reaction compound with carbon bisulpbide.

16. The process of making a vulcanization. accelerator which comprises reacting a mono-basic aromatic organic acid with a secondary amine, andthen reacting the resulting reaction compound with carbon bisulphide. I

1'7. The process of making a vulcanization acceierator which comprises reacting a mono-basic organic acid with a secondary aliphatic amine, and then reacting the resultingreaction compound with carbon bisulphide.

18. The process of making a vulcanization accelerator which comprises reacting a mono-basic aliphatic organic acid with a secondary amine, and then reacting the resulting reaction compound with carbon bisulphide.

CHARLES O. MISERENTINO. 

